22-04-2019, 07:55 AM
My two-penn'orth: Paint has two effects on bolted joints
1. It can act as a lubricant under the joint face; this means that for a given applied torque the axial clamp force may be higher. However I don't imagine blue paint is significantly different from black in this regard!
2. If applied thickly, the joint may relax after a period of time as the paint layer compresses, reducing the axial clamp force. For this reason it's always wise to retighten such joints after a short period of time.
I routinely apply 20lbft to head joints, on occasions have gone up to 22lbft, but never higher.
1. It can act as a lubricant under the joint face; this means that for a given applied torque the axial clamp force may be higher. However I don't imagine blue paint is significantly different from black in this regard!
2. If applied thickly, the joint may relax after a period of time as the paint layer compresses, reducing the axial clamp force. For this reason it's always wise to retighten such joints after a short period of time.
I routinely apply 20lbft to head joints, on occasions have gone up to 22lbft, but never higher.